Plastic carrying case for use with skatewheel conveyers

ABSTRACT

A molded plastic carrying case for use with skatewheel conveyors having outwardly projecting external ribs over substantially the entire base to define an array of geometrically shaped substantially identical recesses whose maximum crosssectional dimension is equal to a function of the distance between each axle of the skatewheel conveyor. The recesses can take various forms and the two preferred shapes disclosed are circular and square-shaped recesses.

United States Patent 1 Box [54] PLASTIC CARRYING CASE FOR USE WITH SKATEWHEEL CONVEYERS [76] Inventor: Theodor M. Box, 1108 Aileen Road,

Brielle, NJ. 08730 [22] Filed: Feb. 16, 1971 [21] Appl. No.: 115,500

Related US. Application Data [63] Continuation of Ser. No. 807,302, March 14, 1969,

abandoned.

[52] US. Cl. ..l93/35 R, 220/21 [51] In, or. ..B65g 13/00 [58] Field oi Search ..193/35; 220/2l, 66, 67, 97

[56] References Cited 0 I I UNITED STATES PATENTS 3,353,703 11/1967 Bartoo et al ..220/2l [111 3,724,628 a [451 Apr. 3, 1973 3,391,815 3,568,879 13/1971 Box ..220/97 Primary Examiner-Even C. 'Blunk Assistant Examiner-Merle F. Maffei Att0rneyKenyon & Kenyon Reilly Carr & Chapin [57] 7 ABSTRACT A molded plastic carrying case for use with skatewheel conveyors having outwardly projecting external ribs over substantially the entire base to define an array of geometrically shaped substantially identi cal recesses whose maximum crosss'ectional dimension is equal to a function of the distance between each axle of the skate'wheel conveyor. The recesses can take various forms and the two preferred shapes disclosed are circular and square-shaped recesses.

5 Claims, 8 Drevvln'g Figures 7/1968 Box 1220/21 BACKGROUND OF THE INVENTION 1. Field Of The Invention This invention relates to a plastic storage case for use with skatewheel conveyors.

2. State Of The Prior Art Skatewheel conveyors are extensively used in place of solid roller, belt or chain conveyors, because of their reduced weight and cost. The conveyors comprise a ladder-like structure formed of two parallel rails or side bars with a series of equidistant, parallel axles mounted perpendicular to each side bar and spanning the space between the side bars. The skatewheels in turn are mountedin a row on the axles parallel to the side bars and each other. The spacing between each skatewheelin a row is usually chosen to be equal to the distance between each axle. Each adjacent row of skatewheels, however, is laterally displaced one-half this same distance, i.e., the distance between each row of skatewheels. This lateral displacement places each skatewheel on the alternate rows of skatewheels in line with each other, and parallel to the side bars. By designing the conveyor in this manner a firm supporting surface is provided for a case or other object on the conveyor.

The skatewheel conveyor while having distinct advantages, does, however, present a problem. Because all objects transported on the conveyor are supported solely by the contact points between the skatewheels and the case, each case must have a flush surfacecapable of smoothly sliding over the rollers. If, however, the bottom of a case is indented or uneven the skatewheels will catch in the indentations and the case will be twisted off the conveyor. Further, if the case is completely smooth, any forces striking the case will tend to rotate the case off the conveyor. These problems require constant supervision and adjustment of the cases on the conveyor and thereby present serious operational disadvantages.

A prior attempt to avoid the problems associated with skatewheel conveyors and plastic cases for use with them is shown in US Pat. No. 3,391,815 which teaches the use of a plastic bottle case having a series of circular projections and reinforcing ribs. This case, in-

Another more specific object is to provide a plastic case which will provide continuous alignment of the case on the conveyor, substantially independent of external forces such as vibrations or blows.

DESCRIPTION OF THE DRAWINGS Other features and objects of the invention will become apparent in the following description, claims and drawings in which:

, FIG. 1 is a diagrammatic plan view of a skatewheel conveyor and storage case superimposed upon the'conveyor;

FIG. 2 is an isometric view showing a plastic case constructed in accordance with the principles of this invention; 7

FIG. 3 is a side view of FIG. 1, showing the operation of a case manufactured according to this invention on a skatewheel conveyor;

FIG. 4 is a bottom view of a case illustrating the unique case construction of this invention;

FIG. 5 is a partial vertical longitudinal view of the case of FIG. 2;

FIG. 6 is an enlarged fragmentary view, showing the construction of the bottom of the case according to this invention and the relationship of the bottom with the skatewheels of the conveyor;

FIG. 7 is a view similar'to FIG. 6, showing another form of the invention; and I I FIG. 8 is a modification of the invention shown in FIG. 6.

DETAILED DESCRIPTION OF THE INvENTIoN As indicated above, the invention involves a plastic storage or carrying. case adapted for use with skatewheel conveyors. As shown in FIGS. 4, .6 and 8, the surface of a case which rests upon the conveyor is composed of a series of externalribs projecting from the base of the case to define an array of geometrically shaped substantially identical recesses thereinul have found that by arranging the ribs. to form identical tended to hold bottles, required reinforcing ribs and a series of shallow depressions to allow stacking of bottle-filled cases on top of each other. The present invention represents an improvement over US. Pat. No. 3,391 ,815 by utilizing a series of ribs to define an array of geometrical recesses on thebase of the case. The

dimensions and shape of the ribs are chosen as a func-' tion ofth'edistance between the skatewheels to provide a unique system of contact points between the caseand the skatewheels.

SUMMARY OF THEINVENTION recesses in parallel rows and columns and byselecting the maximum crosssectional dimension, D, of the recesses as a function of the spacing between the skatewheels in a row (the same as between adjacent rows of wheels), the points of contact between the ribs and the skatewheels in any one row will beeither at the same point on the periphery of the rib or equally divided between two analogous points on the periphery of the ribs. By this particular design, the case is evenly supported upon the conveyor belt and resists any external forces which would rotate the case on the conveyor. Furthenby the unique symmetry obtained from the design of the case, the points of contact between the ribs and the skatewheels always remain constant regardless of any rotation of the case. Thus, the case during its travel along the conveyor" is firmlysupported upon the conveyor in any position, and automatically realigned whenever it is subjected to external rotating forces. Further,the cases designed according to thisinvention have a tendency to resist any rotating forces striking the case. I

Referring to FIG. 1 the numerals 10 and 11 designate the side bars of a wheel conveyor fitted with equidistant axles 12 upon which are mounted the equidistant rotating skatewheels 13. As shown in FIG. 7

3, the conveyor is normally operated at an angle to the horizontal to allow the case to gravitationally slide down the conveyor. As can be seen from the figure, the wheels of the alternate rows are laterally displaced relative to one another to provide a bearing surface for a case or container 14. As shown in FIG. 6, the lateral displacement of the wheels in the alternate rows is at the mid-point of the distance between the skatewheels in the row above or below each respective row. In this manner every other row has skatewheels parallel to each other.

The case 14 shown in FIGS. 2 and 3 may be of any suitable type having a bottom 15, sides 16 and ends 17. It is preferably molded as a single unit from high impact plastic, such as' polyethylene, polypropylene, PVC (polyvinyl chloride), etc. The case may also be provided with carrying holes 18 and openings 19 designed to save material and reduce both weight and costs.

The bottom wall of the case 14 is formed of a series of outwardly projecting external ribs 20, extending over substantially the entire base 15 and aligned in contiguous relationship with each other. The ribs, in the preferred embodiment shown in FIGS. 4, 6 and 8, form an array of recesses having a circular cross-section. I have found that by using these ribs and by selecting the diameter of the recesses as a fraction of the distance between rows of skatewheels (or the distance between the skatewheels in a row), the points of contact between the edge surface of the ribs and the skatewheels in any one row will be either at the same point on the circumference of the ribs or equally divided between two analogous points. In the preferred embodiment shown in FIG. 6, the distance between the skatewheels on the conveyor is selected by the manufacturer of the conveyor. I have found, however, that if the diameter of the recess is made equal to approximately two-thirds the distance between the wheels in a row (or the distance between rows), I achieve the unique resultsof my invention. Thus, as shown in FIG. 6, the ribs define an array of substantially identical recessed portions having a maximum cross-sectional dimension equal to two-thirds the distance between each axle. Further, the ribs are arranged, as shown in FIG. 6, in a plurality of adjacent columns 20a, 20b, 20c and 20d, and rows 20a. The rows, in turn, are parallel to the side edges of the bottom and the columns are parallel to the end edges of the bottom.

As shown in FIG. 6, taking the diameter of the recesses 20 as D, the distance between skatewheels and between rows of skatewheels is one and one-half D. Furthermore, in this designof conveyor the diameter of the wheels will usually either be one-half or threefourths the distance between the wheels. By designing the case in this manner, as shown in FIG. 6, one result is that the wheels in a row contact or rest on the ribs at the same point. This is shown in FIG. 6 where wheels 13b are in contact with the ribs 200, at exactly the same point, 300, throughout the row. As also shown in FIG. 6, if the diameter is selected in the manner described above, the wheels in a row will either contact the ribs at the same point (as explained above) or alternate between two analogous points in a row. As shown, wheels 13a, contact ribs 20a and 20b at points 30a and 30b, respectively. Similarly, each alternate wheel in this row, a, is in contact with the ribs 20a and 20b at the identical points on the ribs of that row.

Thus, in operation should the case be rotated it automatically assumes a position in which the case is firmly supported upon the skatewheels and where the points of contact between the base of the case and the conveyor are either the same or equally divided between two analogous points. In this manner the case is always properly aligned on the conveyor irrespective of exterior impact or other forces.

By the design of the case in the manner described, all contact between the skatewheels and the case in each respective row is made at points either precisely the same or analogous. As a result, one possible theory is that alternate wheels in any row tend to resist rotation of the case by force lines which are in opposite directions. Further, because the contact between the case and the skatewheels is concentrated over a small area, any rotational forces caused by external forces must overcome substantial frictional forces. By this design there is, therefore, a tendency for the case to remain on the conveyor and to resist any forces which tend to vary the case from its projected path. This results in a-rigid and firm positioning of the case upon the conveyor substantially independent of exterior forces acting on the case.

The arrangement shown in FIG. 6 has the further advantage that a case will be evenly supported during its travel along the conveyor, because the ribs 20 are in contact with a sufficient number of conveyor wheels evenly distributed over the bottom wall of the case to prevent canting. In this manner the case is held in a relatively stable condition during itsftravel down the conveyor. Further, the symmetrical design of the circu lar-shaped ribs 20a, 20c and 20d of FIG. 6 also permits placing the case at an angle with respect to the axis of the conveyor and does not require any initial alignment of the case on the conveyor. Thus, by virtue of this unique feature of the case, it will maintain its position on the conveyor irrespective of its initial positioning.

The relative dimensions can, and shown by FIGS. 6 and 8, maybe varied within limits without substantially changing the results obtained by this invention. In practice, it has been found that the wheel spacing distance may vary between one to one and three-quarter times the diameter of the recesses and the spacing distance between the rows of wheels may vary between one and one-half to two times the diameter of the recesses. The distance between the centerpoint of the recesses and the center of the skatewheels may vary between onequarter to one-half the diameter of the recesses, while the wheel diameter may vary between one-half to one times the diameter. Furthermore, thewidth W of the wheels may be about three times the wall thickness w of the ribs.

FIG. 7 illustrates the use of ribs 21a, 21b and 210 in place of the circular recesses 20a, 20b and 200 shown in FIG. 6. In this particular embodiment the external ribs extend diagonally across the bottom in spaced relationship at'substantially 45 angles to the side and end edges. By mounting the ribs to the base in this fashion a lattice work of substantially square, identical sized portions are defined on said base, each having a diagonal equal to approximately two-thirds the distance between each axle. As shown in FIG. 7, the reference D represents the diagonal dimension of the square-shaped recesses. In operation the function and result obtained by use of ribs of this design is substantiallysimilar to that obtained by the use of the case shown in FIG. 6. With this construction, however, it is advisable to initially align the case on the conveyor by placing the case so that alternating wheels in each row engage sides of the recesses forming equal and opposite angles with the wheels in the manner shown in FIG. 7.

FIG. 8 shows a modification of FIG. 6, differing from the latter by the staggering distance of one-half D between adjacent rows of wheels. Again, a detailed analysis shows the operation of the case on a conveyor to maintain alignment and stabilization of the case, in the same manner described and explained above.

In the foregoing, the invention has been described in reference to specific exemplary embodiments. It will be evident, however, that variations and modifications, as well as the substitution of equivalent constructions and arrangements for those shown for illustration, may be made without departing from the broader scope and spirit of the invention as set forth in the appended claims. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense.

What is claimed is:

l. A molded plastic case adapted for use with a skatewheel conveyor having equidistant skatewheels rotatively mounted on a series of axles mounted between a pair of parallel rails, said conveyor of the type in which the distance between the skatewheels on any axle is approximately equal to the predetermined constant distance between each axle and the alternating rows of skatewheels are laterally displaced one-half said distance, I

' said case comprising a pair of side and end walls and a base, said side walls and end walls joined to said base along side and end edges respectively,

said base including a plurality of outwardly projecting substantially identical external ribs extending over substantially the entire base and alignedv in contiguous relationship, said ribs defining an array of geometrically shaped substantially identical recessed portions therein having a maximum cross-sectional dimension equal to approximately two-thirds the distance between each axle of said conveyor to provide a supporting base for stabilized transport of said case on said skatewheel conveyor. I

2. An integrally molded case as set forth in claim 1, wherein said external ribs are of circular configuration defining circular recesses each having a diameter equal to approximately two-thirds the distance between each axle of said conveyor, and aligned in a plurality of adjacent columns and rows, said rows being substantially parallel to the side edges of said bottom and said columns being substantially parallel to the end edges of said bottom.

3. An integrally molded case as set forth in claim 1, wherein said external ribs extend diagonally across said bottom in spaced relationship at substantially 45 angles to said side and end edges to provide a lattice work of adjacent substantially square recessed portions therein of substantially identical size, each having a diagonal equal to approximately two-thirds the distance between each axle of said conveyor, and the outer corners of said lattice work extending to the periphery of said bottom.

4. An integrally molded case as set forth in claim 1,

wherein the external ribs have a wall thickness equal to approximately one-tenth the" distance between the axles of the skatewheel conveyor.

5. An integrally molded case as set forth in claim 1,- 

1. A molded plastic case adapted for use with a skatewheel conveyor having equidistant skatewheels rotatively mounted on a series of axles mounted between a pair of parallel rails, said conveyor of the type in which the distance between the skatewheels on any axle is approximately equal to the predetermined constant distance between each axle and the alternating rows of skatewheels are laterally displaced one-half said distance, said case comprising a pair of side and end walls and a base, said side walls and end walls joined to said base along side and end edges respectively, said base including a plurality of outwardly projecting substantially identical external ribs extending over substantially the entire base and aligned in contiguous relationship, said ribs defining an array of geometrically shaped substantially identical recessed portions therein having a maximum cross-sectional dimension equal to approximately twothirds the distance between each axle of said conveyor to provide a supporting base for stabilized transport of said case on said skatewheel conveyor.
 2. An integrally molded case as set forth in claim 1, wherein said external ribs are of circular configuration defining circular recesses each having a diameter equal to approximately two-thirds the distance between each axle of said conveyor, and aligned in a plurality of adjacent columns and rows, said rows being substantially parallel to the side edges of said bottom and said columns being substantially parallel to the end edges of said bottom.
 3. An integrally molded case as set forth in claim 1, wherein said external ribs extend diagonally across said bottom in spaced relationship at substantially 45* angles to said side and end edges to provide a lattice work of adjacent substantially square recessed portions therein of substantially identical size, each having a diagonal equal to approximately two-thirds the distance between each axle of said conveyor, and the outer corners of said lattice work extending to the periphery of said bottom.
 4. An integrally molded case as set forth in claim 1, wherein the external ribs have a wall thickness equal to approximately one-tenth the distance between the axles of the skatewheel conveyor.
 5. An integrally molded case as set forth in claim 1, wherein the recessed portions have a maximum cross-sectional dimension in a range varying from the distance between each axle of said conveyor to one-half said distance. 